Molecular Imaging Helps in Detection of Breast Cancer

A novel imaging technique seems to be better than standard mammography at detecting breast cancer in high-risk women with dense breast tissue, according to findings from a study involving 940 women.

Molecular breast imaging detected three times as many cancers as mammography did in this group of women, Carrie B. Hruska, Ph.D., said at a media briefing on Sept. 3 that was held in advance of the American Society of Clinical Oncology's annual Breast Cancer Symposium.

“Molecular breast imaging may be a promising adjunct to screening mammography for women with dense breasts and who are at increased risk,” she said. It is estimated that roughly a quarter of women 40 years and older have dense breast patterns.

Molecular breast imaging (MBI) relies on increased uptake of the radiotracer Tc-99m sestamibi by cancer cells, compared with healthy breast tissue, to identify tumors that might go undetected by conventional mammography, according to Dr. Hruska, a research fellow in radiology at the Mayo Clinic in Rochester, Minn.

For the investigation, a total of 940 women underwent mammography and molecular breast imaging.

All of the participants had previously been determined to have mammographically dense breasts and had at least one cancer risk factor, including personal or family history, genetic mutation, previous precancerous finding, a history of chest irradiation, or elevated risk by Gail model.

For MBI, the women were injected with 740 MBq of Tc-99m sestamibi. The location of accumulated radiotracer was then detected using two opposing semiconductor-based gamma cameras. The novel dual-camera configuration was developed at the Mayo Clinic and the sestamibi tracer was supplied by Bristol-Myers Squibb Co.

Craniocaudal and mediolateral oblique views of each breast were obtained (10 minutes per view). The MBIs were read by two radiologists, who were blinded to the mammographic interpretation and all ancillary patient information.

Breast cancer status for each participant was determined using a combination of pathology findings and clinical and/or imaging findings within a 15-month follow-up period.

In all, 13 cancers were diagnosed in 12 patients. Eight cancers were detected by MBI alone, two by both techniques, and two by mammography alone.

In the subset of 375 patients for whom more than 15 months of follow-up had passed since they had MBI, the sensitivity of MBI was 75%, compared with 25% for mammography. The specificity of MBI was 93%, compared with 91% for mammography.

Of the 17 biopsies prompted by mammography in 1.8% of patients, 18% were found to be positive for cancer (positive predictive value).

In comparison, of 36 biopsies that were prompted by MBI in 3.5% of patients, 28% were found to be positive for cancer (positive predictive value).

“To put this in context, probably somewhere in the range of 10%–15% of all breast cancers are clinically occult on mammography. … That is a more common problem in women who have dense breasts,” said moderator Dr. Eric Winer, who is the director of the Breast Oncology Center at the Dana-Farber Cancer Institute in Boston.

MBI was developed based on incidental findings on myocardial perfusion scans, which use Tc-99m sestamibi.

“The reason that MBI [was investigated for] breast imaging is that during cardiac scans in women, people noticed that there was uptake in breast cancers,” Dr. Hruska said.

Tumor uptake of the tracer appears to be “somewhat related to mitochondrial activity, but nobody really knows the true mechanism,” she added.

The researchers are also looking at alternative tracers. “One of them is very exciting. It actually is taken up in tumors based on their angiogenesis, so we think we can find even smaller cancers,” Dr. Hruska said.

The researchers disclosed that they had no conflicts of interest relevant to their study.

Molecular breast imaging (right) found a tumor (bottom arrow) that was not seen on standard mammography (left). Images courtesy Dr. Carrie B. Hruska

A novel imaging technique seems to be better than standard mammography at detecting breast cancer in high-risk women with dense breast tissue, according to findings from a study involving 940 women.

Molecular breast imaging detected three times as many cancers as mammography did in this group of women, Carrie B. Hruska, Ph.D., said at a media briefing on Sept. 3 that was held in advance of the American Society of Clinical Oncology's annual Breast Cancer Symposium.

“Molecular breast imaging may be a promising adjunct to screening mammography for women with dense breasts and who are at increased risk,” she said. It is estimated that roughly a quarter of women 40 years and older have dense breast patterns.

Molecular breast imaging (MBI) relies on increased uptake of the radiotracer Tc-99m sestamibi by cancer cells, compared with healthy breast tissue, to identify tumors that might go undetected by conventional mammography, according to Dr. Hruska, a research fellow in radiology at the Mayo Clinic in Rochester, Minn.

For the investigation, a total of 940 women underwent mammography and molecular breast imaging.

All of the participants had previously been determined to have mammographically dense breasts and had at least one cancer risk factor, including personal or family history, genetic mutation, previous precancerous finding, a history of chest irradiation, or elevated risk by Gail model.

For MBI, the women were injected with 740 MBq of Tc-99m sestamibi. The location of accumulated radiotracer was then detected using two opposing semiconductor-based gamma cameras. The novel dual-camera configuration was developed at the Mayo Clinic and the sestamibi tracer was supplied by Bristol-Myers Squibb Co.

Craniocaudal and mediolateral oblique views of each breast were obtained (10 minutes per view). The MBIs were read by two radiologists, who were blinded to the mammographic interpretation and all ancillary patient information.

Breast cancer status for each participant was determined using a combination of pathology findings and clinical and/or imaging findings within a 15-month follow-up period.

In all, 13 cancers were diagnosed in 12 patients. Eight cancers were detected by MBI alone, two by both techniques, and two by mammography alone.

In the subset of 375 patients for whom more than 15 months of follow-up had passed since they had MBI, the sensitivity of MBI was 75%, compared with 25% for mammography. The specificity of MBI was 93%, compared with 91% for mammography.

Of the 17 biopsies prompted by mammography in 1.8% of patients, 18% were found to be positive for cancer (positive predictive value).

In comparison, of 36 biopsies that were prompted by MBI in 3.5% of patients, 28% were found to be positive for cancer (positive predictive value).

“To put this in context, probably somewhere in the range of 10%–15% of all breast cancers are clinically occult on mammography. … That is a more common problem in women who have dense breasts,” said moderator Dr. Eric Winer, who is the director of the Breast Oncology Center at the Dana-Farber Cancer Institute in Boston.

MBI was developed based on incidental findings on myocardial perfusion scans, which use Tc-99m sestamibi.

“The reason that MBI [was investigated for] breast imaging is that during cardiac scans in women, people noticed that there was uptake in breast cancers,” Dr. Hruska said.

Tumor uptake of the tracer appears to be “somewhat related to mitochondrial activity, but nobody really knows the true mechanism,” she added.

The researchers are also looking at alternative tracers. “One of them is very exciting. It actually is taken up in tumors based on their angiogenesis, so we think we can find even smaller cancers,” Dr. Hruska said.

The researchers disclosed that they had no conflicts of interest relevant to their study.

Molecular breast imaging (right) found a tumor (bottom arrow) that was not seen on standard mammography (left). Images courtesy Dr. Carrie B. Hruska

A novel imaging technique seems to be better than standard mammography at detecting breast cancer in high-risk women with dense breast tissue, according to findings from a study involving 940 women.

Molecular breast imaging detected three times as many cancers as mammography did in this group of women, Carrie B. Hruska, Ph.D., said at a media briefing on Sept. 3 that was held in advance of the American Society of Clinical Oncology's annual Breast Cancer Symposium.

“Molecular breast imaging may be a promising adjunct to screening mammography for women with dense breasts and who are at increased risk,” she said. It is estimated that roughly a quarter of women 40 years and older have dense breast patterns.

Molecular breast imaging (MBI) relies on increased uptake of the radiotracer Tc-99m sestamibi by cancer cells, compared with healthy breast tissue, to identify tumors that might go undetected by conventional mammography, according to Dr. Hruska, a research fellow in radiology at the Mayo Clinic in Rochester, Minn.

For the investigation, a total of 940 women underwent mammography and molecular breast imaging.

All of the participants had previously been determined to have mammographically dense breasts and had at least one cancer risk factor, including personal or family history, genetic mutation, previous precancerous finding, a history of chest irradiation, or elevated risk by Gail model.

For MBI, the women were injected with 740 MBq of Tc-99m sestamibi. The location of accumulated radiotracer was then detected using two opposing semiconductor-based gamma cameras. The novel dual-camera configuration was developed at the Mayo Clinic and the sestamibi tracer was supplied by Bristol-Myers Squibb Co.

Craniocaudal and mediolateral oblique views of each breast were obtained (10 minutes per view). The MBIs were read by two radiologists, who were blinded to the mammographic interpretation and all ancillary patient information.

Breast cancer status for each participant was determined using a combination of pathology findings and clinical and/or imaging findings within a 15-month follow-up period.

In all, 13 cancers were diagnosed in 12 patients. Eight cancers were detected by MBI alone, two by both techniques, and two by mammography alone.

In the subset of 375 patients for whom more than 15 months of follow-up had passed since they had MBI, the sensitivity of MBI was 75%, compared with 25% for mammography. The specificity of MBI was 93%, compared with 91% for mammography.

Of the 17 biopsies prompted by mammography in 1.8% of patients, 18% were found to be positive for cancer (positive predictive value).

In comparison, of 36 biopsies that were prompted by MBI in 3.5% of patients, 28% were found to be positive for cancer (positive predictive value).

“To put this in context, probably somewhere in the range of 10%–15% of all breast cancers are clinically occult on mammography. … That is a more common problem in women who have dense breasts,” said moderator Dr. Eric Winer, who is the director of the Breast Oncology Center at the Dana-Farber Cancer Institute in Boston.

MBI was developed based on incidental findings on myocardial perfusion scans, which use Tc-99m sestamibi.

“The reason that MBI [was investigated for] breast imaging is that during cardiac scans in women, people noticed that there was uptake in breast cancers,” Dr. Hruska said.

Tumor uptake of the tracer appears to be “somewhat related to mitochondrial activity, but nobody really knows the true mechanism,” she added.

The researchers are also looking at alternative tracers. “One of them is very exciting. It actually is taken up in tumors based on their angiogenesis, so we think we can find even smaller cancers,” Dr. Hruska said.

The researchers disclosed that they had no conflicts of interest relevant to their study.

Molecular breast imaging (right) found a tumor (bottom arrow) that was not seen on standard mammography (left). Images courtesy Dr. Carrie B. Hruska